The present invention may be related, for example, to the 3rd Generation Partnership Project (3GPP) Evolved Packet System (EPS) and to the corresponding standard(s). In particular, the present invention may relate to the core network nodes Serving Gateway (SGW) and Mobility Management Entity (MME), or Serving General Packet Radio Service (GPRS) Support Node (SGSN) in the case of Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN) access or Global System for Mobile Communications (GSM) Enhanced Data Rates for GSM Evolution (EDGE) Radio Access Network (GERAN) access, as well as the User Equipment (UE).
FIG. 1 shows the above entities in a simplified view of the EPS network architecture. As shown in FIG. 1, a network 100 comprises a UE 101, an evolved nodeB (eNB) 1021, a Security Gateway (SEG) 1021a, an MME 1023, an SGSN 1023a, an SGW 1025, a Packet Data Network (PDN) Gateway (PGW) 1027, a Policy Charging and Rules Function (PCRF) 1025b, Internet Protocol (IP) services 1025c of a network operator, an Autonomous System (AS) border router (ASBR) or Peering point 1025d, a Home Subscriber Server (HSS) 1028, and the Internet 103. FIG. 1 further shows, by the dashes crossing the lines inter-connecting all entities, the interfaces used between the entities (for example, between SGW 1025 and PGW 1027, an S5 interface is used).
In the 3GPP EPS architecture, the traffic to and from the UE 101 is routed through the RAN, possibly through the SEG 1021a, the SGW 1025 and the PGW 1027, as shown by the thick line in FIG. 1.
The selection of the eNB 1021 is governed by radio conditions. The SEG selection is simply a consequence of the eNB selection, since the SEG has to be used, to which the eNB is connected to.
The SGW 1025 and the PGW 1027 are selected by the MME 1023 based on different criteria that may be classified into “hard” and “soft” criteria:                A “hard” selection criterion is a criterion that must be fulfilled by the selected node. For instance, a selected PGW 1027 must support the Access Point Name (APN) that is associated with the concerned PDN connection and a selected SGW 1025 must serve the area (cell/eNB) where the UE 101 is located.        A “soft” selection criterion is a criterion that may or may not be fulfilled. Soft criteria can often be fulfilled to a varying degree—the more the better. Examples that are applicable to selection of both the SGW 1025 and PGW 1027 include path optimization (e.g. topological closeness), possibilities of SGW 1025 and PGW 1027 in the same node (indicated in FIG. 1 by a thin dashed line surrounding the blocks of SGW 1025 and PGW 1027) and load balancing.        
Selection of SGW 1025/PGW 1027 takes place in the network whenever a SGW 1025 and/or a PGW 1027 needs to be allocated to the UE 101, either to serve a new PDN connection (i.e. a new APN) or to replace a previously allocated SGW. There are three cases in which selection of the SGW 1025/PGW 1027 is triggered:                Attach (which includes establishment of an initial PDN connection and default bearer):                    In this selection case, both SGW 1025 and PGW 1027 are selected.                        SGW Relocation:                    In this selection case, only the SGW 1025 is selected, while the PGW(s) remain(s) fixed.                        Additional PDN Connection Establishment (for an additional APN):                    In this selection case, only a PGW 1027 is selected, while the already allocated SGW 1025 remains.                        
The PGW 1027 acts as a mobility anchor and a point of presence for the UE 101. Thus, once a PGW 1027 is selected during attach of UE 101 or new PDN connection establishment towards an APN, the same PGW 1027 will be used irrespective of the UE 101 movements until the UE 101 is detached or the PDN connection is disconnected.
The SGW 1025 is selected for the default bearer at network Attach operation. A UE 101 can only have a single SGW 1025 allocated at a time, so the same SGW 1025 is used also for subsequent bearers, irrespective of the APN. In contrast to the PGW 1027, the SGW 1025 allocated to a UE 101 may change over the time: this is called SGW relocation.
A SGW 1025 may serve a limited part of the area of a Public Land Mobile Network (PLMN) (i.e. a limited fraction of the eNBs in the PLMN), denoted SGW Service Area (SA). SGW SAs are a collection of complete Tracking Areas (TAs). A Service Area is served by one or more SGWs 1025 in parallel. Service Areas may also overlap each other. Thus, an obvious reason of SGW relocation is UE mobility, i.e., SGW relocation is needed because the current SGW 1025 does not serve a new eNB 1021 to which the UE 101 has moved.
The standard (for example, 3GPP Technical Specification (TS) 23.401, V9.1.0) specifies two types of procedures that may involve SGW relocation:                One is the handover with SGW relocation; there are two possible procedures, the procedure for S1-based handover shown in FIG. 2 and the procedure for X2-based handover is shown in FIG. 3. Note that Long Term Evolution (LTE) specific procedures are shown, however, corresponding handover procedures exist for GERAN and UTRAN specified in TS 23.060 not shown here.        The other procedure is the Tracking Area Update (TAU) with SGW relocation, which is shown in FIG. 4. Note that this figure is also LTE-specific, however, for GERAN and UTRAN, the corresponding Routing Area Update (RAU) is defined in TS 23.060.        
Accordingly, FIG. 2 depicting the S1-based handover with SGW relocation, shows a network having the UE 101, a source eNB 1021, a target eNB 1022, a source MME 1023, a target MME 1024, a source SGW 1025, a target SGW 1026, the PGW 1027 and the HSS 1028. FIG. 3 depicting the X2-based handover with SGW relocation, basically shows, with the exception of only one MME 1023 being present and the HSS 1028 being left out, the same entities as FIG. 2. FIG. 4 depicting the TAU with SGW relocation shows, with the extension that the source (or old) MME 1023 may also be an SGSN 1023 and the presence of PCRF 1029, the same entities as FIG. 2. Note that FIGS. 2 to 4 stem from the above-cited 3GPP TS 23.401, V9.1.0.
As a summary, current system procedures in the 3GPP Evolved Packet Core (specified, for example, in TS 23.401 and 23.060) allow for the relocation of the SGW 1025 during mobility events (such as handovers and tracking or routing area updates), but there is currently no possibility to relocate the SGW 1025 without using one of the mobility related procedures. This has been considered sufficient so far since it has not been expected that there are reasons but mobility to change SGWs 1025, 1026.
Another area of interest is enterprise networks which recently have gained increasing interest where multiple Home (evolved) nodeBs (H(e)NBs) may be deployed. In enterprise networks, a local GW node may also be deployed with the aim of providing Local IP Access (LIPA) towards the enterprise network. The following solutions have been proposed to address that scenario.                Serving GW Relocation Approach:                    In that solution, the SGW 1025 is relocated into the local GW, so that the local GW takes on the roles of both the SGW 1025 and the PGW 1027 in the architecture (see, for example, 3GPP draft S2-102180). That allows for the reuse of the existing system architecture and procedures, while at the same time provides for local connections to the enterprise network without traversing the mobile operator network with user plane traffic.                        Direct Tunnel with User Plane Only Interface:                    Another alternative is to define a new direct tunnel solution where data is being sent directly between the H(e)NBs in the enterprise and the PGW 1027 in the enterprise. That can be realized either via updating the signalling interfaces S11, S4 and S5 in the operator's network (see, for example, 3GPP draft S2-102432).                        Direct Tunnel with User and Control Plane Interface:                    A variant of the previous solution is that a new signalling interface is also defined between the H(e)NB and PGW so that the impact on S11, S4 and S5 is avoided (see, for example, 3GPP draft S2-102433).                        